The present invention is related in general to the field of semiconductor device assembly and packaging, and more specifically to fabricating integrated circuit (IC) devices having flexible tape substrates.
A flexible tape substrate is typically composed of polymer material such as polyimide, and is often referred to as a polyimide tape substrate or simply as a film substrate. The polyimide tape substrate is typically fabricated by disposing an adhesive material layered between a polyimide layer and a metal layer. As a first step, a surface of a polyimide layer is covered with a film adhesive that is protected by a removable, protective plastic sheet. After punching holes at desired locations, the protective sheet covering the adhesive layer is peeled off, thereby exposing the adhesive surface. A thin copper foil is laminated to the adhesive surface, thereby creating a 3-layer polyimide/adhesive/copper flexible tape substrate having multiple holes in the polyimide layer and no holes in the copper foil.
The adhesive material, which is often soft and sticky, is typically difficult to handle as it tends to stick to the processing equipment such as a punch and die set and also tends to extrude (e.g., stretch during punching). In addition, the adhesive material may be squeezed into a lumen or cavity of the punched hole due to the pressure applied during the lamination of the copper foil. Presence of adhesive material in the lumen of the punched hole may disrupt subsequent metal deposition in the holes, and may potentially lead to the formation of voids at the plug base or formation of defective plug surfaces.